Hydrothermal origin of platinum-group mineralization in low-temperature copper sulfide-rich assemblages, Salt Chuck Intrusion, Alaska

Watkinson, David H.; Melling, David R.

doi:10.2113/gsecongeo.87.1.175

Cited by 43 publications

(20 citation statements)

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“…These parameters are consistent with Au and Cu mobilization via Clcomplexes (Davidson and Large 1994). Cl-complexes are also efficient in transporting PGE, Hg and Ag in oxidized and acid hydrothermal solutions (Mountain andWood 1988, Watkinson andMelling 1992).…”

Section: Supergene Alterationsupporting

confidence: 68%

The Serra Leste Sediment-Hosted Au-(Pd-Pt) Mineralization, Carajás Province

TALLARICO

COIMBRA

Costa

2000

RBG

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The Serra Leste Au-(Pt-Pd) mineralization is hosted by a folded low-grade metasedimentary sequence known as Rio Fresco Formation. The orebodies are located at the hinge zone of a recumbent syncline at the contact between carbonaceous metasiltstone and dolomitic marble. Ore mineralogy includes quartz, kaolinite, goethite, Mn-oxides, muscovite, amorphous carbon together with gold, Pd-Pt-(Hg) minerals and minor Cu-Co-Ni-sulfides. The orebodies are oxidized, and hypogene mineralization is not known beyond the base of supergene alteration. The widespread occurrence of the actinolite-calcite pair and the local association with diopside, indicate a minimum of 550°C for peak metamorphic temperature of the dolomitic marble. This temperature is inconsistent with the low-grade metamorphic assemblage of metasiltstones, thence with regional metamorphism, and is better accommodated in a thermal-aureole hypothesis. Cooling of the aureole triggered the breakdown of actinolite to calcite + quartz, at temperatures of about 400-450°C. Later hydrothermal activity, between 230°C and 360°C, developed chlorite alteration and sulfide precipitation in both dolomitic marble and diorite intrusion(s) that crosscut the metasedimentary sequence. The carbonaceous metasiltstone possibly acted as a chemical barrier, triggering focused deposition of precious metals through a rapid decrease of the oxidation conditions of the hydrothermal fluid. This process was possibly coupled with carbonate dissolution of dolomitic marble that triggered open-space-filling processes, developed an external jasperoid envelope around the orebodies and caused a pH increase.

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Section: Supergene Alterationsupporting

confidence: 68%

The Serra Leste Sediment-Hosted Au-(Pd-Pt) Mineralization, Carajás Province

TALLARICO

COIMBRA

Costa

2000

RBG

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“…There are, however, rare reports of comparable fluids in association with precious metal deposits including unconformity-type Au-PtPd-U mineralization (Mernagh et al, 1994), low-temperature Cu-Au-Pd-Ag deposits (Watkinson and Melling, 1992), and the unusual Prairie-type precious metal mineralization reported from western Canada Feng and Abercrombie, 1994).…”

Section: Discussionmentioning

confidence: 99%

“…Maximum solubilities are observed under near-neutral, relatively reduced conditions, where bisulfide complexes dominate gold transport, or under highly acidic, oxidizing conditions where chloride transport can occur (e.g., Seward, 1993). The latter mechanism has been invoked to explain brine-associated gold in several settings (Watkinson and Melling, 1992;Feng and Abercrombie, 1994;Mernagh et al, 1994). These environments show evidence of either very low sulfur fugacities or extremely oxidizing conditions, both of which favor chloride transport.…”

Section: Discussionmentioning

confidence: 99%

Gold remobilization by low-temperature brines; evidence from the Curraghinalt gold deposit, Northern Ireland

Wilkinson¹,

Boyce²,

Earls³

et al. 1999

Economic Geology

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“…The occurrence of biotite, chlorite and amphibole inter-grown with sulphides is additional evidence of volatile activity (Farrow and Watksinson, 1999). Post-crystallisation alteration of primary Ni-Cu sulphides led to the formation of Cu-rich ores, accompanied by exotic phases such as Pt-and Pd-rich arsenides, tellurides and Bi-bearing minerals (Watkinson and Melling, 1992;Farrow and Watkinson, 1999). These minerals are also associated with hydrous silicates (e.g.…”

Section: Discussionmentioning

confidence: 99%

Geological and geochemical characteristics of the Baimazhai Ni-Cu-(PGE) sulphide deposit in Yunnan, China

Chuan-jie

De-xian

Nian

et al. 2007

Chin. J. of Geochem.

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The sulphide ores of the Baimazhai deposit, although typically orthomagmatic, locally exhibit peculiar textural features and are intimately associated with hydrothermal minerals, such as biotite, amphibole and chlorite. This association suggests that the magmatic sulphide ores were subjected to hydrothermal alteration and subsequent redistribution, resulting in the observed textural features. Geochemically, the Baimazhai sulphide ores are enriched in Cu, Pd and Au, which according to previous studies, reflects the action of hydrothermal fluids. Interestingly, Ar-Ar dating yielded the plateau ages of about 160-170 Ma, which are at odds with the established Permian age of the Emeishan large igneous province. We interpreted these younger ages as due to thermal resetting during post-Permian tectonothermal events. We have proposed a model in which tectonic movements and hydrothermal fluids related to these events modified the pre-existing magmatic sulphides. Given the degree of overprint, we suggested two possible scenarios: 1) the sulphide disseminations that surround the massive magmatic ores are the result of deformation and hydrothermal alteration; and 2) there were both magmatic massive and disseminated sulphides, in which case the scale and relocation of remobilization would have been smaller, but still detectable.

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Hydrothermal origin of platinum-group mineralization in low-temperature copper sulfide-rich assemblages, Salt Chuck Intrusion, Alaska

Cited by 43 publications

References 0 publications

The Serra Leste Sediment-Hosted Au-(Pd-Pt) Mineralization, Carajás Province

The Serra Leste Sediment-Hosted Au-(Pd-Pt) Mineralization, Carajás Province

Gold remobilization by low-temperature brines; evidence from the Curraghinalt gold deposit, Northern Ireland

Geological and geochemical characteristics of the Baimazhai Ni-Cu-(PGE) sulphide deposit in Yunnan, China

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